Help with XML case logic

Hey guys,I'm trying to develop a multi-function display as part of an aircraft project, but I'm having issues finding the best way to implement a menu-driven system. If MS would just release an XML SDK life would be alot easier:)What I'm trying to do and have one gauge with a number of buttons along all sides which corespond different pages. So what I need is a good system for case logic to keep things tidy, and to store the current page in a variable, along with some logic to decide which "function" of the gauge to branch to based on the options available for the current page.Those of you who have seen a military MFD/DDI will know I'm trying to do. Sounds simple, but I'm tearing my hair out trying to hack up default gauges like the GPS in order to find a logical and readable system for turning on and off gauge functions.For example:Main menu (top level) Navigation Main menu Nav option 1 Nav option 2 Etc... HSI Main Menu HSI option 1 HSI option 2 Etc... Ect...My question is, what would the syntax look like to nest the various gauge functions based on which button get pushed?Should I use CASE, or MACRO(like they've been doing for the buttons in the GPS gauge)?If anyone has a code snippet that I could use as a starting point, it would be greatly appreciated!Jon